Surgical Tools Facilitating Increased Accuracy, Speed and Simplicity in Performing Joint Arthroplasty

ABSTRACT

Disclosed herein are tools for repairing articular surfaces repair materials and for repairing an articular surface. The surgical tools are designed to be customizable or highly selectable by patient to increase the speed, accuracy and simplicity of performing total or partial arthroplasty.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 11/002,573 for“PATIENT SELECTABLE JOINT ARTHROPLASTY DEVICES AND SURGICAL TOOLSFACILITATING INCREASED ACCURACY, SPEED AND SIMPLICITY IN PERFORMINGTOTAL AND PARTIAL JOINT ARTHROPLASTY” filed Dec. 2, 2004, which in turnis a continuation-in-part of U.S. Ser. No. 10/724,010 for “PATIENTSELECTABLE JOINT ARTHROPLASTY DEVICES AND SURGICAL TOOLS FACILITATINGINCREASED ACCURACY, SPEED AND SIMPLICITY IN PERFORMING TOTAL AND PARTIALJOINT ARTHROPLASTY” filed Nov. 25, 2003 which in turn is acontinuation-in-part of U.S. Ser. No. 10/305,652 entitled “METHODS ANDCOMPOSITIONS FOR ARTICULAR REPAIR,” filed Nov. 27, 2002, which is acontinuation-in-part of U.S. Ser. No. 10/160,667, filed May 28, 2002,which in turn claims the benefit of U.S. Ser. No. 60/293,488 entitled“METHODS TO IMPROVE CARTILAGE REPAIR SYSTEMS”, filed May 25, 2001, U.S.Ser. No. 60/363,527, entitled “NOVEL DEVICES FOR CARTILAGE REPAIR, filedMar. 12, 2002 and U.S. Ser. Nos. 60/380,695 and 60/380,692, entitled“METHODS AND COMPOSITIONS FOR CARTILAGE REPAIR,” and “METHODS FOR JOINTREPAIR,”, filed May 14, 2002, all of which applications are herebyincorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to methods, systems and devices forarticular resurfacing. The present invention includes surgical moldsdesigned to achieve optimal cut planes in a joint in preparation forinstallation of a joint implant.

BACKGROUND ART

A variety of tools are available to assist surgeons in performing jointsurgery. In the knee, for example, U.S. Pat. No. 4,501,266 to McDanielissued Feb. 26, 1985 discloses a knee distraction device thatfacilitates knee arthroplasty. The device has an adjustable forcecalibration mechanism that enables the device to accommodate controlledselection of the ligament-tensioning force to be applied to therespective, opposing sides of the knee. U.S. Pat. No. 5,002,547 toPoggie et al. issued Mar. 26, 1991 discloses a modular apparatus for usein preparing the bone surface for implantation of a modular total kneeprosthesis. The apparatus has cutting guides, templates, alignmentdevices along with a distractor and clamping instruments that providemodularity and facilitate bone resection and prosthesis implantation.U.S. Pat. No. 5,250,050 to Poggie et al. issued Oct. 5, 1993 is alsodirected to a modular apparatus for use in preparing a bone surface forthe implantation of a modular total knee prosthesis. U.S. Pat. No.5,387,216 to Thornhill et al. issued Feb. 7, 1995 disclosesinstrumentation for use in knee revision surgery. A bearing sleeve isprovided that is inserted into the damaged canal in order to take upadditional volume. The rod passes through the sleeve and is positionedto meet the natural canal of the bone. The rod is then held in a fixedposition by the bearing sleeve. A cutting guide can then be mounted onthe rod for cutting the bone and to provide a mounting surface for theimplant. U.S. Pat. No. 6,056,756 to Eng et al. issued May 2, 2000discloses a tool for preparing the distal femoral end for a prostheticimplant. The tool lays out the resection for prosthetic replacement andincludes a jack for pivotally supporting an opposing bone such that thejack raises the opposing bone in flexion to the spacing of the intendedprosthesis. U.S. Pat. No. 6,106,529 to Techiera issued Aug. 22, 2000discloses an epicondylar axis referencing drill guide for use inresection to prepare a bone end for prosthetic joint replacement. U.S.Pat. No. 6,296,646 to Williamson issued Oct. 2, 2001 discloses a systemthat allows a practitioner to position the leg in the alignment that isdirected at the end of the implant procedure and to cut both the femurand tibia while the leg is fixed in alignment. U.S. Pat. No. 6,620,168to Lombardi et al. issued Sep. 16, 2003 discloses a tool forintermedullary revision surgery along with tibial components.

U.S. Pat. No. 5,578,037 to Sanders et al. issued Nov. 26, 1996 disclosesa surgical guide for femoral resection. The guide enables a surgeon toresect a femoral neck during a hip arthroplasty procedure so that thefemoral prosthesis can be implanted to preserve or closely approximatethe anatomic center of rotation of the hip.

Currently available tools do not always enable the surgeon to make themost accurate cuts on the bone surface in preparing the target joint forimplantation.

Thus, there remains a need for tools that improve the accuracy of thejoint resurfacing process.

SUMMARY OF THE INVENTION

In an aspect of the invention, surgical tools for preparing a joint toreceive an implant are described, for example a tool comprising one ormore surfaces or members that conform at least partially to the shape ofthe articular surfaces of the joint (e.g., a femoral condyle and/ortibial plateau of a knee joint). In certain embodiments, the toolcomprises Lucite silastic and/or other polymers or suitable materials.The tool can be re-useable or single-use. The tool can be comprised of asingle component or multiple components. In certain embodiments, thetool comprises an array of adjustable, closely spaced pins.

The tool comprises: a mold having a surface for engaging a jointsurface; a block that communicates with the mold; and at least one guideaperture in the block. Another tool is disclosed that is formed at leastpartially in situ and comprises: a mold formed in situ using at leastone of an inflatable hollow device or a retaining device to conform tothe joint surface on at least one surface having a surface for engaginga joint surface; a block that communicates with the mold; and at leastone guide aperture in the block.

In any of the embodiments and aspects described herein, the joint can bea knee, shoulder, hip, vertebrae, elbow, ankle, wrist etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying drawings, in which:

FIG. 1A illustrates a femur, tibia and fibula along with the mechanicaland anatomic axes. FIGS. 1B-E illustrate the tibia with the anatomic andmechanical axis used to create a cutting plane along with a cut femurand tibia. FIG. 1F illustrates the proximal end of the femur includingthe head of the femur.

FIG. 2 shows an example of a surgical tool having one surface matchingthe geometry of an articular surface of the joint. Also shown is anaperture in the tool capable of controlling drill depth and width of thehole and allowing implantation of an insertion of implant having apress-fit design.

FIG. 3 is a flow chart depicting various methods of the invention usedto create a mold for preparing a patient's joint for arthroscopicsurgery.

FIG. 4A depicts, in cross-section, an example of a surgical toolcontaining an aperture through which a surgical drill or saw can fit.The aperture guides the drill or saw to make the proper hole or cut inthe underlying bone. Dotted lines represent where the cut correspondingto the aperture will be made in bone. FIG. 4B depicts, in cross-section,an example of a surgical tool containing apertures through which asurgical drill or saw can fit and which guide the drill or saw to makecuts or holes in the bone. Dotted lines represent where the cutscorresponding to the apertures will be made in bone.

FIGS. 5A-Q illustrate tibial cutting blocks and molds used to create asurface perpendicular to the anatomic axis for receiving the tibialportion of a knee implant.

FIGS. 6A-O illustrate femur cutting blocks and molds used to create asurface for receiving the femoral portion of a knee implant.

FIG. 7A-G illustrate patellar cutting blocks and molds used to preparethe patella for receiving a portion of a knee implant.

FIG. 8A-H illustrate femoral head cutting blocks and molds used tocreate a surface for receiving the femoral portion of a knee implant.

FIG. 9A-D illustrate acetabulum cutting blocks and molds used to createa surface for a hip implant.

FIG. 10A illustrates a patella modeled from CT data. FIGS. 10B-Dillustrate a mold guide, and then the mold guide placed on an articularsurface of the patella. FIG. 10E illustrates a drill placed into apatella through mold drill guide. FIG. 10F illustrates a reamer used toprepare the patella.

FIG. 11A illustrates a reamer made for each patella size. FIG. 11Billustrates a reamed patella ready for patella implantation.

FIG. 12A-F illustrate a recessed patella implanted on a patella.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The following description is presented to enable any person skilled inthe art to make and use the invention. Various modifications to theembodiments described will be readily apparent to those skilled in theart, and the generic principles defined herein can be applied to otherembodiments and applications without departing from the spirit and scopeof the present invention as defined by the appended claims. Thus, thepresent invention is not intended to be limited to the embodimentsshown, but is to be accorded the widest scope consistent with theprinciples and features disclosed herein. To the extent necessary toachieve a complete understanding of the invention disclosed, thespecification and drawings of all issued patents, patent publications,and patent applications cited in this application are incorporatedherein by reference.

As will be appreciated by those of skill in the art, the practice of thepresent invention employs, unless otherwise indicated, conventionalmethods of x-ray imaging and processing, x-ray tomosynthesis, ultrasoundincluding A-scan, B-scan and C-scan, computed tomography (CT scan),magnetic resonance imaging (MRI), optical coherence tomography, singlephoton emission tomography (SPECT) and positron emission tomography(PET) within the skill of the art. Such techniques are explained fullyin the literature and need not be described herein. See, e.g., X-RayStructure Determination: A Practical Guide, 2nd Edition, editors Stoutand Jensen, 1989, John Wiley & Sons, publisher; Body C T: A PracticalApproach, editor Slone, 1999, McGraw-Hill publisher; X-ray Diagnosis: APhysician's Approach, editor Lam, 1998 Springer-Verlag, publisher; andDental Radiology: Understanding the X-Ray Image, editor LaetitiaBrocklebank 1997, Oxford University Press publisher. See also, TheEssential Physics of Medical Imaging (2.sup.nd Ed.), Jerrold T.Bushberg, et al.

As described herein, repair systems, including surgical instruments,guides and molds, of various sizes, curvatures and thicknesses can beobtained. These repair systems, including surgical instruments, guidesand molds, can be catalogued and stored to create a library of systemsfrom which an appropriate system for an individual patient can then beselected. In other words, a defect, or an articular surface, is assessedin a particular subject and a pre-existing repair system, includingsurgical instruments, guides and molds, having a suitable shape and sizeis selected from the library for further manipulation (e.g., shaping)and implantation.

Performing a total knee arthroplasty is a complicated procedure. Inreplacing the knee with an artificial knee, it is important to get theanatomical and mechanical axes of the lower extremity aligned correctlyto ensure optimal functioning of the implanted knee.

As shown in FIG. 1A, the center of the hip 102 (located at the head 130of the femur 132), the center of the knee 104 (located at the notchwhere the intercondular tubercle 134 of the tibia 136 meet the femur)and ankle 106 lie approximately in a straight line 110 which defines themechanical axis of the lower extremity. The anatomic axis 120 aligns5-7° offset θ from the mechanical axis in the valgus, or outward,direction.

The long axis of the tibia 136 is collinear with the mechanical axis ofthe lower extremity 110. From a three-dimensional perspective, the lowerextremity of the body ideally functions within a single plane known asthe median anterior-posterior plane (MAP-plane) throughout theflexion-extension arc. In order to accomplish this, the femoral head130, the mechanical axis of the femur, the patellar groove, theintercondylar notch, the patellar articular crest, the tibia and theankle remain within the MAP-plane during the flexion-extension movement.During movement, the tibia rotates as the knee flexes and extends in theepicondylar axis which is perpendicular to the MAP-plane.

A variety of image slices can be taken at each individual joint, e.g.,the knee joint 150-150 _(n), and the hip joint 152-150 _(n). These imageslices can be used as described above in Section I along with an imageof the full leg to ascertain the axis.

With disease and malfunction of the knee, alignment of the anatomic axisis altered. Performing a total knee arthroplasty is one solution forcorrecting a diseased knee. Implanting a total knee joint, such as thePFC Sigma RP Knee System by Johnson & Johnson, requires that a series ofresections be made to the surfaces forming the knee joint in order tofacilitate installation of the artificial knee. The resections should bemade to enable the installed artificial knee to achieveflexion-extension movement within the MAP-plane and to optimize thepatient's anatomical and mechanical axis of the lower extremity.

First, the tibia 130 is resected to create a flat surface to accept thetibial component of the implant. In most cases, the tibial surface isresected perpendicular to the long axis of the tibia in the coronalplane, but is typically sloped 4-7° posteriorly in the sagittal plane tomatch the normal slope of the tibia. As will be appreciated by those ofskill in the art, the sagittal slope can be 0° where the device to beimplanted does not require a sloped tibial cut. The resection line 158is perpendicular to the mechanical axis 110, but the angle between theresection line and the surface plane of the plateau 160 varies dependingon the amount of damage to the knee.

FIGS. 1B-D illustrate an anterior view of a resection of an anatomicallynormal tibial component, a tibial component in a varus knee, and atibial component in a valgus knee, respectively. In each figure, themechanical axis 110 extends vertically through the bone and theresection line 158 is perpendicular to the mechanical axis 110 in thecoronal plane, varying from the surface line formed by the jointdepending on the amount of damage to the joint. FIG. 1B illustrates anormal knee wherein the line corresponding to the surface of the joint160 is parallel to the resection line 158. FIG. 1C illustrates a varusknee wherein the line corresponding to the surface of the joint 160 isnot parallel to the resection line 158. FIG. 1D illustrates a valgusknee wherein the line corresponding to the surface of the joint 160 isnot parallel to the resection line 158.

Once the tibial surface has been prepared, the surgeon turns topreparing the femoral condyle.

The plateau of the femur 170 is resected to provide flat surfaces thatcommunicate with the interior of the femoral prosthesis. The cuts madeto the femur are based on the overall height of the gap to be createdbetween the tibia and the femur. Typically, a 20 mm gap is desirable toprovide the implanted prosthesis adequate room to achieve full range ofmotion. The bone is resected at a 5-7° angle valgus to the mechanicalaxis of the femur. Resected surface 172 forms a flat plane with anangular relationship to adjoining surfaces 174, 176. The angle θ′, θ″between the surfaces 172-174, and 172-176 varies according to the designof the implant.

As illustrated in FIG. 1F, the external geometry of the proximal femurincludes the head 180, the neck 182, the lesser trochanter 184, thegreater trochanter 186 and the proximal femoral diaphysis. The relativepositions of the trochanters 184, 186, the femoral head center 102 andthe femoral shaft 188 are correlated with the inclination of theneck-shaft angle. The mechanical axis 110 and anatomic axis 120 are alsoshown. Assessment of these relationships can change the reamingdirection to achieve neutral alignment of the prosthesis with thefemoral canal.

Using anteroposterior and lateral radiographs, measurements are made ofthe proximal and distal geometry to determine the size and optimaldesign of the implant.

Typically, after obtaining surgical access to the hip joint, the femoralneck 182 is resected, e.g. along the line 190. Once the neck isresected, the medullary canal is reamed. Reaming can be accomplished,for example, with a conical or straight reamer, or a flexible reamer.The depth of reaming is dictated by the specific design of the implant.Once the canal has been reamed, the proximal reamer is prepared byserial rasping, with the rasp directed down into the canal.

Further, surgical assistance can be provided by using a device appliedto the outer surface of the articular cartilage or the bone, includingthe subchondral bone, in order to match the alignment of the articularrepair system and the recipient site or the joint. The device can beround, circular, oval, ellipsoid, curved or irregular in shape. Theshape can be selected or adjusted to match or enclose an area ofdiseased cartilage or an area slightly larger than the area of diseasedcartilage or substantially larger than the diseased cartilage. The areacan encompass the entire articular surface or the weight bearingsurface. Such devices are typically preferred when replacement of amajority or an entire articular surface is contemplated.

Mechanical devices can be used for surgical assistance (e.g., surgicaltools), for example using gels, molds, plastics or metal. One or moreelectronic images or intraoperative measurements can be obtainedproviding object coordinates that define the articular and/or bonesurface and shape. These objects' coordinates can be utilized to eithershape the device, e.g. using a CAD/CAM technique, to be adapted to apatient's articular anatomy or, alternatively, to select a typicallypre-made device that has a good fit with a patient's articular anatomy.The device can have a surface and shape that will match all or portionsof the articular or bone surface and shape, e.g. similar to a “mirrorimage.” The device can include apertures, slots and/or holes toaccommodate surgical instruments such as drills, reamers, curettes,k-wires, screws and saws.

Typically, a position will be chosen that will result in an anatomicallydesirable cut plane, drill hole, or general instrument orientation forsubsequent placement of an articular repair system or for facilitatingplacement of the articular repair system. Moreover, the device can bedesigned so that the depth of the drill, reamer or other surgicalinstrument can be controlled, e.g., the drill cannot go any deeper intothe tissue than defined by the device, and the size of the hole in theblock can be designed to essentially match the size of the implant.Information about other joints or axis and alignment information of ajoint or extremity can be included when selecting the position of theseslots or holes. Alternatively, the openings in the device can be madelarger than needed to accommodate these instruments. The device can alsobe configured to conform to the articular shape. The apertures, oropenings, provided can be wide enough to allow for varying the positionor angle of the surgical instrument, e.g., reamers, saws, drills,curettes and other surgical instruments. An instrument guide, typicallycomprised of a relatively hard material, can then be applied to thedevice. The device helps orient the instrument guide relative to thethree-dimensional anatomy of the joint.

The surgeon can, optionally, make fine adjustments between the alignmentdevice and the instrument guide. In this manner, an optimal compromisecan be found, for example, between biomechanical alignment and jointlaxity or biomechanical alignment and joint function, e.g. in a kneejoint flexion gap and extension gap. By oversizing the openings in thealignment guide, the surgeon can utilize the instruments and insert themin the instrument guide without damaging the alignment guide. Thus, inparticular if the alignment guide is made of plastic, debris will not beintroduced into the joint. The position and orientation between thealignment guide and the instrument guide can be also be optimized withthe use of, for example, interposed spacers, wedges, screws and othermechanical or electrical methods known in the art.

A surgeon may desire to influence joint laxity as well as jointalignment. This can be optimized for different flexion and extension,abduction, or adduction, internal and external rotation angles. For thispurpose, for example, spacers can be introduced that are attached orthat are in contact with one or more molds. The surgeon canintraoperatively evaluate the laxity or tightness of a joint usingspacers with different thickness or one or more spacers with the samethickness. For example, spacers can be applied in a knee joint in thepresence of one or more molds and the flexion gap can be evaluated withthe knee joint in flexion. The knee joint can then be extended and theextension gap can be evaluated. Ultimately, the surgeon will select anoptimal combination of spacers for a given joint and mold. A surgicalcut guide can be applied to the mold with the spacers optionallyinterposed between the mold and the cut guide. In this manner, the exactposition of the surgical cuts can be influenced and can be adjusted toachieve an optimal result. Someone skilled in the art will recognizeother means for optimizing the position of the surgical cuts. Forexample, expandable or ratchet-like devices can be utilized that can beinserted into the joint or that can be attached or that can touch themold. Hinge-like mechanisms are applicable. Similarly, jack-likemechanisms are useful. In principal, any mechanical or electrical deviceuseful for fine-tuning the position of the cut guide relative to themolds can be used.

A surgeon may desire to influence joint laxity as well as jointalignment. This can be optimized for different flexion and extension,abduction, or adduction, internal and external rotation angles. For thispurpose, for example, spacers can be introduced that are attached orthat are in contact with one or more molds. The surgeon canintraoperatively evaluate the laxity or tightness of a joint usingspacers with different thickness or one or more spacers with the samethickness. For example, spacers can be applied in a knee joint in thepresence of one or more molds and the flexion gap can be evaluated withthe knee joint in flexion. The knee joint can then be extended and theextension gap can be evaluated. Ultimately, the surgeon will select anoptimal combination of spacers for a given joint and mold. A surgicalcut guide can be applied to the mold with the spacers optionallyinterposed between the mold and the cut guide. In this manner, the exactposition of the surgical cuts can be influenced and can be adjusted toachieve an optimal result. Someone skilled in the art will recognizeother means for optimizing the position of the surgical cuts. Forexample, expandable or ratchet-like devices can be utilized that can beinserted into the joint or that can be attached or that can touch themold. Hinge-like mechanisms are applicable. Similarly, jack-likemechanisms are useful. In principal, any mechanical or electrical deviceuseful for fine-tuning the position of the cut guide relative to themolds can be used.

The molds and any related instrumentation such as spacers or ratchetscan be combined with a tensiometer to provide a better intraoperativeassessment of the joint. The tensiometer can be utilized to furtheroptimize the anatomic alignment and tightness of the joint and toimprove post-operative function and outcomes. Optionally local contactpressures may be evaluated intraoperatively, for example using a sensorlike the ones manufactured by Tekscan, South Boston, Mass.

The mold or alignment guide can be made of a plastic or polymer. Inother embodiments, the mold or portions of the mold can be made ofmetal. Metal inserts may be applied to plastic components. For example,a plastic mold may have an opening to accept a reaming device or a saw.A metal insert may be used to provide a hard wall to accept the reameror saw. Using this or similar designs can be useful to avoid theaccumulation of plastic or other debris in the joint when the saw orother surgical instruments may get in contact with the mold.

The molds may not only be used for assisting the surgical technique andguiding the placement and direction of surgical instruments. Inaddition, the molds can be utilized for guiding the placement of theimplant or implant components. For example, in the hip joint, tilting ofthe acetabular component is a frequent problem with total hiparthroplasty. A mold can be applied to the acetabular wall with anopening in the center large enough to accommodate the acetabularcomponent that the surgeon intends to place. The mold can havereceptacles or notches that match the shape of small extensions that canbe part of the implant or that can be applied to the implant. Forexample, the implant can have small members or extensions applied to thetwelve o'clock and six o'clock positions. See, for example, FIG. 9A-D,discussed below. By aligning these members with notches or receptaclesin the mold, the surgeon can ensure that the implant is inserted withouttilting or rotation. These notches or receptacles can also be helpful tohold the implant in place while bone cement is hardening in cementeddesigns.

One or more molds can be used during the surgery. For example, in thehip, a mold can be initially applied to the proximal femur that closelyapproximates the 3D anatomy prior to the resection of the femoral head.The mold can include an opening to accommodate a saw (see FIGS. 8-9).The opening is positioned to achieve an optimally placed surgical cutfor subsequent reaming and placement of the prosthesis. A second moldcan then be applied to the proximal femur after the surgical cut hasbeen made. The second mold can be useful for guiding the direction of areamer prior to placement of the prosthesis. As can be seen in this, aswell as in other examples, molds can be made for joints prior to anysurgical intervention. However, it is also possible to make molds thatare designed to fit to a bone or portions of a joint after the surgeonhas already performed selected surgical procedures, such as cutting,reaming, drilling, etc. The mold can account for the shape of the boneor the joint resulting from these procedures.

In certain embodiments, the surgical assistance device comprises anarray of adjustable, closely spaced pins (e.g., plurality ofindividually moveable mechanical elements). One or more electronicimages or intraoperative measurements can be obtained providing objectcoordinates that define the articular and/or bone surface and shape.These objects' coordinates can be entered or transferred into thedevice, for example manually or electronically, and the information canbe used to create a surface and shape that will match all or portions ofthe articular and/or bone surface and shape by moving one or more of theelements, e.g. similar to an “image.” The device can include slots andholes to accommodate surgical instruments such as drills, cureftes,k-wires, screws and saws. The position of these slots and holes can beadjusted by moving one or more of the mechanical elements. Typically, aposition will be chosen that will result in an anatomically desirablecut plane, reaming direction, or drill hole or instrument orientationfor subsequent placement of an articular repair system or forfacilitating the placement of an articular repair system. Informationabout other joints or axis and alignment information

FIG. 2 shows an example of a surgical tool 200 having one surface 210matching the geometry of an articular surface of the joint. Also shownis an aperture 215 in the tool 200 capable of controlling drill depthand width of the hole and allowing implantation or insertion of implant220 having a press-fit design.

In another embodiment, a frame can be applied to the bone or thecartilage in areas other than the diseased bone or cartilage. The framecan include holders and guides for surgical instruments. The frame canbe attached to one or preferably more previously defined anatomicreference points. Alternatively, the position of the frame can becross-registered relative to one, or more, anatomic landmarks, using animaging test or intraoperative measurement, for example one or morefluoroscopic images acquired intraoperatively. One or more electronicimages or intraoperative measurements including using mechanical devicescan be obtained providing object coordinates that define the articularand/or bone surface and shape. These objects' coordinates can be enteredor transferred into the device, for example manually or electronically,and the information can be used to move one or more of the holders orguides for surgical instruments. Typically, a position will be chosenthat will result in a surgically or anatomically desirable cut plane ordrill hole orientation for subsequent placement of an articular repairsystem. Information about other joints or axis and alignment informationof a joint or extremity can be included when selecting the position ofthese slots or holes.

Furthermore, re-useable tools (e.g., molds) can be also be created andemployed. Non-limiting examples of re-useable materials include puttiesand other deformable materials (e.g., an array of adjustable closelyspaced pins that can be configured to match the topography of a jointsurface). In other embodiments, the molds may be made using balloons.The balloons can optionally be filled with a hardening material. Asurface can be created or can be incorporated in the balloon that allowsfor placement of a surgical cut guide, reaming guide, drill guide orplacement of other surgical tools. The balloon or other deformablematerial can be shaped intraoperatively to conform to at least onearticular surface. Other surfaces can be shaped in order to be parallelor perpendicular to anatomic or biomechanical axes. The anatomic orbiomechanical axes can be found using an intraoperative imaging test orsurgical tools commonly used for this purpose in hip, knee or otherarthroplasties.

In these embodiments, the mold can be created directly from the jointduring surgery or, alternatively, created from an image of the joint,for example, using one or more computer programs to determine objectcoordinates defining the surface contour of the joint and transferring(e.g., dialing-in) these co-ordinates to the tool. Subsequently, thetool can be aligned accurately over the joint and, accordingly, thesurgical instrument guide or the implant will be more accurately placedin or over the articular surface.

In both single-use and re-useable embodiments, the tool can be designedso that the instrument controls the depth and/or direction of the drill,i.e., the drill cannot go any deeper into the tissue than the instrumentallows, and the size of the hole or aperture in the instrument can bedesigned to essentially match the size of the implant. The tool can beused for general prosthesis implantation, including, but not limited to,the articular repair implants described herein and for reaming themarrow in the case of a total arthroplasty.

These surgical tools (devices) can also be used to remove an area ofdiseased cartilage and underlying bone or an area slightly larger thanthe diseased cartilage and underlying bone. In addition, the device canbe used on a “donor,” e.g., a cadaveric specimen, to obtain implantablerepair material. The device is typically positioned in the same generalanatomic area in which the tissue was removed in the recipient. Theshape of the device is then used to identify a donor site providing aseamless or near seamless match between the donor tissue sample and therecipient site. This can be achieved by identifying the position of thedevice in which the articular surface in the donor, e.g. a cadavericspecimen, has a seamless or near seamless contact with the inner surfacewhen applied to the cartilage.

The device can be molded, machined or formed based on the size of thearea of diseased cartilage and based on the curvature of the cartilageor the underlying subchondral bone or a combination of both. The moldingcan take into consideration surgical removal of, for example, themeniscus, in arriving at a joint surface configuration. The device canthen be applied to the donor, (e.g., a cadaveric specimen) and the donortissue can be obtained with use of a blade or saw or other tissueremoving device. The device can then be applied to the recipient in thearea of the diseased cartilage and the diseased cartilage and underlyingbone can be removed with use of a blade or saw or other tissue cuttingdevice whereby the size and shape of the removed tissue containing thediseased cartilage will closely resemble the size and shape of the donortissue. The donor tissue can then be attached to the recipient site. Forexample, said attachment can be achieved with use of screws or pins(e.g., metallic, non-metallic or bioresorable) or other fixation meansincluding but not limited to a tissue adhesive. Attachment can bethrough the cartilage surface or alternatively, through the marrowspace.

The implant site can be prepared with use of a robotic device. Therobotic device can use information from an electronic image forpreparing the recipient site.

Identification and preparation of the implant site and insertion of theimplant can be supported by a surgical navigation system. In such asystem, the position or orientation of a surgical instrument withrespect to the patient's anatomy can be tracked in real-time in one ormore 2D or 3D images. These 2D or 3D images can be calculated fromimages that were acquired preoperatively, such as MR or CT images.Non-image based surgical navigation systems that find axes or anatomicalstructures, for example with use of joint motion, can also be used. Theposition and orientation of the surgical instrument as well as the moldincluding alignment guides, surgical instrument guides, reaming guides,drill guides, saw guides, etc. can be determined from markers attachedto these devices. These markers can be located by a detector using, forexample, optical, acoustical or electromagnetic signals.

Identification and preparation of the implant site and insertion of theimplant can also be supported with use of a C-arm system. The C-armsystem can afford imaging of the joint in one or, preferably, multipleplanes. The multiplanar imaging capability can aid in defining the shapeof an articular surface. This information can be used to selected animplant with a good fit to the articular surface. Currently availableC-arm systems also afford cross-sectional imaging capability, forexample for identification and preparation of the implant site andinsertion of the implant. C-arm imaging can be combined withadministration of radiographic contrast.

In still other embodiments, the surgical devices described herein caninclude one or more materials that harden to form a mold of thearticular surface. A wide-variety of materials that harden in situ havebeen described above including polymers that can be triggered to undergoa phase change, for example polymers that are liquid or semi-liquid andharden to solids or gels upon exposure to air, application ofultraviolet light, visible light, exposure to blood, water or otherionic changes. (See, also, U.S. Pat. No. 6,443,988 to Felt et al. issuedSep. 3, 2002 and documents cited therein). Non-limiting examples ofsuitable curable and hardening materials include polyurethane materials(e.g., U.S. Pat. No. 6,443,988 to Felt et al., U.S. Pat. No. 5,288,797to Khalil issued Feb. 22, 1994, U.S. Pat. No. 4,098,626 to Graham et al.issued Jul. 4, 1978 and U.S. Pat. No. 4,594,380 to Chapin et al. issuedJun. 10, 1986; and Lu et al. (2000) BioMaterials 21(15):1595-1605describing porous poly(L-lactide acid foams); hydrophilic polymers asdisclosed, for example, in U.S. Pat. No. 5,162,430; hydrogel materialssuch as those described in Wake et al. (1995) Cell Transplantation4(3):275-279, Wiese et al. (2001) J. Biomedical Materials Research54(2):179-188 and Marler et al. (2000) Plastic Reconstruct. Surgery105(6):2049-2058; hyaluronic acid materials (e.g., Duranti et al. (1998)Dermatologic Surgery 24(12):1317-1325); expanding beads such as chitinbeads (e.g., Yusof et al. (2001) J. Biomedical Materials Research54(1):59-68); crystal free metals such as Liquidmetals®, and/ormaterials used in dental applications (See, e.g., Brauer and Antonucci,“Dental Applications” pp. 257-258 in “Concise Encyclopedia of PolymerScience and Engineering” and U.S. Pat. No. 4,368,040 to Weissman issuedJan. 11, 1983). Any biocompatible material that is sufficiently flowableto permit it to be delivered to the joint and there undergo completecure in situ under physiologically acceptable conditions can be used.The material can also be biodegradable.

The curable materials can be used in conjunction with a surgical tool asdescribed herein. For example, the surgical tool can include one or moreapertures therein adapted to receive injections and the curablematerials can be injected through the apertures. Prior to solidifying insitu the materials will conform to the articular surface facing thesurgical tool and, accordingly, will form a mirror image impression ofthe surface upon hardening, thereby recreating a normal or near normalarticular surface. In addition, curable materials or surgical tools canalso be used in conjunction with any of the imaging tests and analysisdescribed herein, for example by molding these materials or surgicaltools based on an image of a joint.

FIG. 3 is a flow chart illustrating the steps involved in designing amold for use in preparing a joint surface. Typically, the first step isto measure the size of the area of the diseased cartilage or cartilageloss 300, Once the size of the cartilage loss has been measured, theuser can measure the thickness of the adjacent cartilage 320, prior tomeasuring the curvature of the articular surface and/or the subchondralbone 330. Alternatively, the user can skip the step of measuring thethickness of the adjacent cartilage 302. Once an understanding anddetermination of the nature of the cartilage defect is determined,either a mold can be selected from a library of molds 332 or a patientspecific mold can be generated 334. In either event, the implantationsite is then prepared 340 and implantation is performed 342. Any ofthese steps can be repeated by the optional repeat steps 301, 321, 331,333, 335, 341.

A variety of techniques can be used to derive the shape of the mold. Forexample, a few selected CT slices through the hip joint, along with afull spiral CT through the knee joint and a few selected slices throughthe ankle joint can be used to help define the axes if surgery iscontemplated of the knee joint. Once the axes are defined, the shape ofthe subchondral bone can be derived, followed by applying standardizedcartilage loss. Other more sophisticated scanning procedures can be usedto derive this information without departing from the scope of theinvention.

Turning now to tools for specific joint applications which are intendedto teach the concept of the design as it would then apply to otherjoints in the body:

When a total knee arthroplasty is contemplated, the patient can undergoan imaging test, as discussed in more detail above, that willdemonstrate the articular anatomy of a knee joint, e.g. width of thefemoral condyles, the tibial plateau etc. Additionally, other joints canbe included in the imaging test thereby yielding information on femoraland tibial axes, deformities such as varus and valgus and otherarticular alignment. The imaging test can be an x-ray image, preferablyin standing, load-bearing position, a CT scan or an MRI scan orcombinations thereof. The articular surface and shape as well asalignment information generated with the imaging test can be used toshape the surgical assistance device, to select the surgical assistancedevice from a library of different devices with pre-made shapes andsizes, or can be entered into the surgical assistance device and can beused to define the preferred location and orientation of saw guides ordrill holes or guides for reaming devices or other surgical instruments.Intraoperatively, the surgical assistance device is applied to thetibial plateau and subsequently the femoral condyle(s) by matching itssurface with the articular surface or by attaching it to anatomicreference points on the bone or cartilage. The surgeon can thenintroduce a reamer or saw through the guides and prepare the joint forthe implantation. By cutting the cartilage and bone along anatomicallydefined planes, a more reproducible placement of the implant can beachieved. This can ultimately result in improved postoperative resultsby optimizing biomechanical stresses applied to the implant andsurrounding bone for the patient's anatomy and by minimizing axismalalignment of the implant. In addition, the surgical assistance devicecan greatly reduce the number of surgical instruments needed for totalor unicompartmental knee arthroplasty. Thus, the use of one or moresurgical assistance devices can help make joint arthroplasty moreaccurate, improve postoperative results, improve long-term implantsurvival, reduce cost by reducing the number of surgical instrumentsused. Moreover, the use of one or more surgical assistance device canhelp lower the technical difficulty of the procedure and can helpdecrease operating room (“OR”) times.

Thus, surgical tools described herein can also be designed and used tocontrol drill alignment, depth and width, for example when preparing asite to receive an implant. For example, the tools described herein,which typically conform to the joint surface, can provide for improveddrill alignment and more accurate placement of any implant. Ananatomically correct tool can be constructed by a number of methods andcan be made of any material, preferably a translucent material such asplastic, Lucite, silastic, SLA or the like, and typically is ablock-like shape prior to molding.

FIG. 4A depicts, in cross-section, an example of a mold 400 for use onthe tibial surface having an upper surface 420. The mold 400 contains anaperture 425 through which a surgical drill or saw can fit. The apertureguides the drill or saw to make the proper hole or cut in the underlyingbone 410 as illustrated in FIGS. 1B-D. Dotted lines 432 illustrate wherethe cut corresponding to the aperture will be made in bone.

FIG. 4B depicts, a mold 408 suitable for use on the femur. As can beappreciated from this perspective, additional apertures are provided toenable additional cuts to the bone surface. The apertures 405 enablecuts 406 to the surface of the femur. The resulting shape of the femurcorresponds to the shape of the interior surface of the femoral implant,typically as shown in FIG. 1E. Additional shapes can be achieved, ifdesired, by changing the size, orientation and placement of theapertures. Such changes would be desired where, for example, theinterior shape of the femoral component of the implant requires adifferent shape of the prepared femur surface.

Turning now to FIG. 5, a variety of illustrations are provided showing atibial cutting block and mold system. FIG. 5A illustrates the tibialcutting block 500 in conjunction with a tibia 502 that has not beenresected. In this depiction, the cutting block 500 consists of at leasttwo pieces. The first piece is a patient specific interior piece 510 ormold that is designed on its inferior surface 512 to mate, orsubstantially mate, with the existing geography of the patient's tibia502. The superior surface 514 and side surfaces 516 of the first piece510 are configured to mate within the interior of an exterior piece 520.The reusable exterior piece 520 fits over the interior piece 510. Thesystem can be configured to hold the mold onto the bone.

The reusable exterior piece has a superior surface 522 and an inferiorsurface 524 that mates with the first piece 510. The reusable exteriorpiece 520 includes cutting guides 528, to assist the surgeon inperforming the tibial surface cut described above. As shown herein aplurality of cutting guides can be provided to provide the surgeon avariety of locations to choose from in making the tibial cut. Ifnecessary, additional spacers can be provided that fit between the firstpatient configured, or molded, piece 510 and the second reusableexterior piece, or cutting block, 520.

The variable nature of the interior piece facilitates obtaining the mostaccurate cut despite the level of disease of the joint because itpositions the exterior piece 520 such that it can achieve a cut that isperpendicular to the mechanical axis. Either the interior piece 510 orthe exterior piece 520 can be formed out of any of the materialsdiscussed above in Section TI, or any other suitable material.Additionally, a person of skill in the art will appreciate that theinvention is not limited to the two piece configuration describedherein. The reusable exterior piece 520 and the patient specificinterior piece 510 can be a single piece that is either patient specific(where manufacturing costs of materials support such a product) or isreusable based on a library of substantially defect conforming shapesdeveloped in response to known or common tibial surface sizes anddefects.

The interior piece 510 is typically molded to the tibia including thesubchondral bone and/or the cartilage. The surgeon will typically removeany residual meniscal tissue prior to applying the mold. Optionally, theinterior surface 512 of the mold can include shape information ofportions or all of the menisci.

Turning now to FIG. 5B-D, a variety of views of the removable exteriorpiece 520. The top surface 522 of the exterior piece can be relativelyflat. The lower surface 524 which abuts the interior piece conforms tothe shape of the upper surface of the interior piece. In thisillustration the upper surface of the interior piece is flat, thereforethe lower surface 524 of the reusable exterior surface is also flat toprovide an optimal mating surface.

A guide plate 526 is provided that extends along the side of at least aportion of the exterior piece 520. The guide plate 526 provides one ormore slots or guides 528 through which a saw blade can be inserted toachieve the cut desired of the tibial surface. Additionally, the slot,or guide, can be configured so that the saw blade cuts at a lineperpendicular to the mechanical axis, or so that it cuts at a line thatis perpendicular to the mechanical axis, but has a 4-7° slope in thesagittal plane to match the normal slope of the tibia.

Optionally, a central bore 530 can be provided that, for example,enables a drill to ream a hole into the bone for the stem of the tibialcomponent of the knee implant.

FIGS. 5E-H illustrate the interior, patient specific, piece 510 from avariety of perspectives. FIG. 55E shows a side view of the piece showingthe uniform superior surface 514 and the uniform side surfaces 516 alongwith the irregular inferior surface 516. The inferior surface mates withthe irregular surface of the tibia 502. FIG. 5F illustrates a superiorview of the interior, patient, specific piece of the mold 510.Optionally having an aperture 530. FIG. 5G illustrates an inferior viewof the interior patient specific mold piece 510 further illustrating theirregular surface which includes convex and concave portions to thesurface, as necessary to achieve optimal mating with the surface of thetibia. FIG. 5H illustrates cross-sectional views of the interior patientspecific mold piece 510. As can be seen in the cross-sections, thesurface of the interior surface changes along its length.

As is evident from the views shown in FIGS. 5B and D, the length of theguide plate 526 can be such that it extends along all or part of thetibial plateau, e.g. where the guide plate 526 is asymmetricallypositioned as shown in FIG. 5B or symmetrical as in FIG. 3D. If totalknee arthroplasty is contemplated, the length of the guide plate 526typically extends along all of the tibial plateau. If unicompartmentalarthroplasty is contemplated, the length of the guide plate typicallyextends along the length of the compartment that the surgeon willoperate on. Similarly, if total knee arthroplasty is contemplated, thelength of the molded, interior piece 510 typically extends along all ofthe tibial plateau; it can include one or both tibial spines. Ifunicompartmental arthroplasty is contemplated, the length of the moldedinterior piece typically extends along the length of the compartmentthat the surgeon will operate on; it can optionally include a tibialspine.

Turning now to FIG. 5I, an alternative embodiment is depicted of theaperture 530. In this embodiment, the aperture features lateralprotrusions to accommodate using a reamer or punch to create an openingin the bone that accepts a stem having flanges.

FIGS. 5J and M depict alternative embodiments of the invention designedto control the movement and rotation of the cutting block 520 relativeto the mold 510. As shown in FIG. 5J a series of protrusions,illustrated as pegs 540, are provided that extend from the superiorsurface of the mold. As will be appreciated by those of skill in theart, one or more pegs or protrusions can be used without departing fromthe scope of the invention. For purposes of illustration, two pegs havebeen shown in FIG. 5J. Depending on the control desired, the pegs 540are configured to fit within, for example, a curved slot 542 thatenables rotational adjustment as illustrated in FIG. 5K or within arecess 544 that conforms in shape to the peg 540 as shown in FIG. 5L. Aswill be appreciated by those of skill in the art, the recess 544 can besized to snugly encompass the peg or can be sized larger than the peg toallow limited lateral and rotational movement.

As illustrated in FIG. 5M the surface of the mold 510 can be configuredsuch that the upper surface forms a convex dome 550 that fits within aconcave well 552 provided on the interior surface of the cutting block520. This configuration enables greater rotational movement about themechanical axis while limiting lateral movement or translation.

Other embodiments and configurations could be used to achieve theseresults without departing from the scope of the invention.

As will be appreciated by those of skill in the art, more than twopieces can be used, where appropriate, to comprise the system. Forexample, the patient specific interior piece 510 can be two pieces thatare configured to form a single piece when placed on the tibia.Additionally, the exterior piece 520 can be two components. The firstcomponent can have, for example, the cutting guide apertures 528. Afterthe resection using the cutting guide aperture 528 is made, the exteriorpiece 520 can be removed and a secondary exterior piece 520′ can be usedwhich does not have the guide plate 526 with the cutting guide apertures528, but has the aperture 530 which facilitates boring into the tibialsurface an aperture to receive a stem of the tibial component of theknee implant. Any of these designs could also feature the surfaceconfigurations shown in FIGS. 5J-M, if desired.

FIG. 5N illustrates an alternative design of the cutting block 520 thatprovides additional structures 560 to protect, for example, the cruciateligaments, from being cut during the preparation of the tibial plateau.These additional structures can be in the form of indented guides 560,as shown in FIG. 5N or other suitable structures.

FIG. 5O illustrates a cross-section of a system having anchoring pegs562 on the surface of the interior piece 510 that anchor the interiorpiece 510 into the cartilage or meniscal area.

FIGS. 5P AND Q illustrate a device 500 configured to cover half of atibial plateau such that it is unicompartmental.

Turning now to FIG. 6, a femoral mold system is depicted thatfacilitates preparing the surface of the femur such that the finallyimplanted femoral implant will achieve optimal mechanical and anatomicalaxis alignment.

FIG. 6A illustrates the femur 600 with a first portion 610 of the moldplaced thereon. In this depiction, the top surface of the mold 612 isprovided with a plurality of apertures. In this instance the aperturesconsist of a pair of rectangular apertures 614, a pair of squareapertures 616, a central bore aperture 618 and a long rectangularaperture 620. The side surface 622 of the first portion 610 also has arectangular aperture 624. Each of the apertures is larger than theeventual cuts to be made on the femur so that, in the event the materialthe first portion of the mold is manufactured from a soft material, suchas plastic, it will not be inadvertently cut during the joint surfacepreparation process. Additionally, the shapes can be adjusted, e.g.,rectangular shapes made trapezoidal, to give a greater flexibility tothe cut length along one area, without increasing flexibility in anotherarea. As will be appreciated by those of skill in the art, other shapesfor the apertures, or orifices, can be changed without departing fromthe scope of the invention.

FIG. 6B illustrates a side view of the first portion 610 from theperspective of the side surface 622 illustrating the aperture 624. Asillustrated, the exterior surface 611 has a uniform surface which isflat, or relatively flat configuration while the interior surface 613has an irregular surface that conforms, or substantially conforms, withthe surface of the femur.

FIG. 6C illustrates another side view of the first, patient specificmolded, portion 610, more particularly illustrating the irregularsurface 613 of the interior. FIG. 6D illustrates the first portion 610from a top view. The center bore aperture 618 is optionally provided tofacilitate positioning the first piece and to prevent central rotation.

FIG. 6D illustrates a top view of the first portion 610. The bottom ofthe illustration corresponds to an anterior location relative to theknee joint. From the top view, each of the apertures is illustrated asdescribed above. As will be appreciated by those of skill in the art,the apertures can be shaped differently without departing from the scopeof the invention.

Turning now to FIG. 6E, the femur 600 with a first portion 610 of thecutting block placed on the femur and a second, exterior, portion 640placed over the first portion 610 is illustrated. The second, exterior,portion 640 features a series of rectangular grooves (642-650) thatfacilitate inserting a saw blade therethrough to make the cuts necessaryto achieve the femur shape illustrated in FIG. 1E. These grooves canenable the blade to access at a 90° angle to the surface of the exteriorportion, or, for example, at a 45° angle. Other angles are also possiblewithout departing from the scope of the invention.

As shown by the dashed lines, the grooves (642-650) of the secondportion 640, overlay the apertures of the first layer.

FIG. 6F illustrates a side view of the second, exterior, cutting blockportion 640. From the side view a single aperture 650 is provided toaccess the femur cut. FIG. 6G is another side view of the second,exterior, portion 640 showing the location and relative angles of therectangular grooves. As evidenced from this view, the orientation of thegrooves 642, 648 and 650 is perpendicular to at least one surface of thesecond, exterior, portion 640. The orientation of the grooves 644, 646is at an angle that is not perpendicular to at least one surface of thesecond, exterior portion 640. These grooves (644, 646) facilitate makingthe angled chamfer cuts to the femur. FIG. 6H is a top view of thesecond, exterior portion 640. As will be appreciated by those of skillin the art, the location and orientation of the grooves will changedepending upon the design of the femoral implant and the shape requiredof the femur to communicate with the implant.

FIG. 6I illustrates a spacer 601 for use between the first portion 610and the second portion 640. The spacer 601 raises the second portionrelative to the first portion, thus raising the area at which the cutthrough groove 624 is made relative to the surface of the femur. As willbe appreciated by those of skill in the art, more than one spacer can beemployed without departing from the scope of the invention. Spacers canalso be used for making the tibial cuts. Optional grooves or channels603 can be provided to accommodate, for example, pins 660 shown in FIG.6J.

Similar to the designs discussed above with respect to FIG. 5,alternative designs can be used to control the movement and rotation ofthe cutting block 640 relative to the mold 610. As shown in FIG. 6J aseries of protrusions, illustrated as pegs 660, are provided that extendfrom the superior surface of the mold. These pegs or protrusions can betelescoping to facilitate the use of molds if necessary. As will beappreciated by those of skill in the art, one or more pegs orprotrusions can be used without departing from the scope of theinvention. For purposes of illustration, two pegs have been shown inFIG. 6J. Depending on the control desired, the pegs 660 are configuredto fit within, for example, a curved slot that enables rotationaladjustment similar to the slots illustrated in FIG. 5K or within arecess that conforms in shape to the peg, similar to that shown in FIG.5L and described with respect to the tibial cutting system. As will beappreciated by those of skill in the art, the recess 662 can be sized tosnugly encompass the peg or can be sized larger than the peg to allowlimited lateral and rotational movement.

As illustrated in FIG. 6K the surface of the mold 610 can be configuredsuch that the upper surface forms a convex dome 664 that fits within aconcave well 666 provided on the interior surface of the cutting block640. This configuration enables greater rotational movement about themechanical axis while limiting lateral movement or translation.

In installing an implant, first the tibial surface is cut using a tibialblock, such as those shown in FIG. 6. The patient specific mold isplaced on the femur. The knee is then placed in extension and spacers670, such as those shown in FIG. 6I, or shims are used, if required,until the joint optimal function is achieved in both extension andflexion. The spacers, or shims, are typically of an incremental size,e.g., 5 mm thick to provide increasing distance as the leg is placed inextension and flexion. A tensiometer can be used to assist in thisdetermination or can be incorporated into the mold or spacers in orderto provide optimal results. The design of tensiometers are known in theart and are not included herein to avoid obscuring the invention.Suitable designs include, for example, those described in U.S. Pat. No.5,630,820 to Todd issued May 20, 1997.

As illustrated in FIGS. 6N (sagittal view) and 6M (coronal view), theinterior surface 613 of the mold 610 can include small teeth 665 orextensions that can help stabilize the mold against the cartilage 666 orsubchondral bone 667.

Turning now to FIG. 7, a variety of illustrations are provided showing apatellar cutting block and mold system. FIGS. 7A-C illustrates thepatellar cutting block 700 in conjunction with a patella 702 that hasnot been resected. In this depiction, the cutting block 700 can consistof only one piece or a plurality of pieces, if desired. The innersurface 703 is patient specific and designed to mate, or substantiallymate, with the existing geography of the patient's patella 702. Smallopenings are present 707 to accept the saw. The mold or block can haveonly one or multiple openings. The openings can be larger than the sawin order to allow for some rotation or other fine adjustments. FIG. 7Ais a view in the sagittal plane A. The quadriceps tendon 704 andpatellar tendon 705 are shown.

FIG. 7B is a view in the axial plane A. The cartilage 706 is shown. Themold can be molded to the cartilage or the subchondral bone orcombinations thereof FIG. 7C is a frontal view F of the molddemonstrating the opening for the saw 707. The dashed line indicates therelative position of the patella 702.

FIGS. 7D (sagittal view) and E (axial view) illustrate a patellarcutting block 708 in conjunction with a patella 702 that has not beenresected. In this depiction, the cutting block 708 consists of at leasttwo pieces. The first piece is a patient specific interior piece 710 ormold that is designed on its inferior surface 712 to mate, orsubstantially mate, with the existing geography of the patient's patella702. The posterior surface 714 and side surfaces 716 of the first piece710 are configured to mate within the interior of an exterior piece 720.The reusable exterior piece 720 fits over the interior piece 710 andholds it onto the patella. The reusable exterior piece has an interiorsurface 724 that mates with the first piece 710. The reusable exteriorpiece 720 includes cutting guides 707, to assist the surgeon inperforming the patellar surface cut. A plurality of cutting guides canbe provided to provide the surgeon a variety of locations to choose fromin making the patellar cut. If necessary, additional spacers can beprovided that fit between the first patient configured, or molded, piece710 and the second reusable exterior piece, or cutting block, 720.

The second reusable exterior piece, or cutting block, 720, can havegrooves 722 and extensions 725 designed to mate with surgicalinstruments such as a patellar clamp 726. The patellar clamp 726 canhave ring shaped graspers 728 and locking mechanisms, for exampleratchet-like 730. The opening 732 in the grasper fits onto the extension725 of the second reusable exterior piece 720. Portions of a firstportion of the handle of the grasper can be at an oblique angle 734relative to the second portion of the handle, or curved (not shown), inorder to facilitate insertion. Typically the portion of the grasper thatwill be facing towards the intra-articular side will have an oblique orcurved shaped thereby allowing a slightly smaller incision.

The variable nature of the interior piece facilitates obtaining the mostaccurate cut despite the level of disease of the joint because itpositions the exterior piece 720 in the desired plane. Either theinterior piece 710 or the exterior piece 720 can be formed out of any ofthe materials discussed above in Section II, or any other suitablematerial. Additionally, a person of skill in the art will appreciatethat the invention is not limited to the two piece configurationdescribed herein. The reusable exterior piece 720 and the patientspecific interior piece 710 can be a single piece that is either patientspecific (where manufacturing costs of materials support such a product)or is reusable based on a library of substantially defect conformingshapes developed in response to known or common tibial surface sizes anddefects.

The interior piece 710 is typically molded to the patella including thesubchondral bone and/or the cartilage.

From this determination, an understanding of the amount of space neededto balance the knee is determined and an appropriate number of spacersis then used in conjunction with the cutting block and mold to achievethe cutting surfaces and to prevent removal of too much bone. Where thecutting block has a thickness of, for example, 10 mm, and each spacerhas a thickness of 5 mm, in preparing the knee for cuts, two of thespacers would be removed when applying the cutting block to achieve thecutting planes identified as optimal during flexion and extension.Similar results can be achieved with ratchet or jack like designsinterposed between the mold and the cut guide.

Turning now to FIG. 8, a variety of views showing sample mold andcutting block systems for use in the hip joint are shown. FIG. 8Aillustrates femur 810 with a mold and cutting block system 820 placed toprovide a cutting plane 830 across the femoral neck 812 to facilitateremoval of the head 814 of the femur and creation of a surface 816 forthe hip ball prosthesis.

FIG. 8B illustrates a top view of the cutting block system 820. Thecutting block system 820 includes an interior, patient specific, moldedsection 824 and an exterior cutting block surface 822. The interior,patient specific, molded section 824 can include a canal 826 tofacilitate placing the interior section 824 over the neck of the femur.As will be appreciated by those of skill in the art, the width of thecanal will vary depending upon the rigidity of the material used to makethe interior molded section. The exterior cutting block surface 822 isconfigured to fit snugly around the interior section. Additionalstructures can be provided, similar to those described above withrespect to the knee cutting block system, that control movement of theexterior cutting block 824 relative to interior mold section 822, aswill be appreciated by those of skill in the art. Where the interiorsection 824 encompasses all or part of the femoral neck, the cuttingblock system can be configured such that it aids in removal of thefemoral head once the cut has been made by, for example, providing ahandle 801.

FIG. 8C illustrates a second cutting block system 850 that can be placedover the cut femur to provide a guide for reaming after the femoral headhas been removed using the cutting block shown in FIG. 8A. FIG. 8D is atop view of the cutting block shown in FIG. 8C. As will be appreciatedby those of skill in the art, the cutting block shown in FIG. 8C-D, canbe one or more pieces. As shown in FIG. 8E, the aperture 852 can beconfigured such that it enables the reaming for the post of the implantto be at a 90° angle relative to the surface of femur. Alternatively, asshown in FIG. 8F, the aperture 852 can be configured to provide an angleother than 90° for reaming, if desired.

FIGS. 9A (sagittal view) and 9B (frontal view, down onto mold)illustrates a mold system 955 for the acetabulum 957. The mold can havegrooves 959 that stabilize it against the acetabular rim 960. Surgicalinstruments, e.g. reamers, can be passed through an opening in the mold956. The side wall of the opening 962 can guide the direction of thereamer or other surgical instruments. Metal sleeves 964 can be insertedinto the side wall 962 thereby protecting the side wall of the mold fromdamage. The metal sleeves 964 can have lips 966 or overhanging edgesthat secure the sleeve against the mold and help avoid movement of thesleeve against the articular surface.

FIG. 9C is a frontal view of the same mold system shown in FIGS. 9A and9B. A groove 970 has been added at the 6 and 12 o'clock positions. Thegroove can be used for accurate positioning or placement of surgicalinstruments. Moreover, the groove can be useful for accurate placementof the acetabular component without rotational error. Someone skilled inthe art will recognize that more than one groove or internal guide canbe used in order to not only reduce rotational error but also errorrelated to tilting of the implant. As seen FIG. 9D, the implant 975 canhave little extensions 977 matching the grooves thereby guiding theimplant placement. The extensions 977 can be a permanent part of theimplant design or they can be detachable. Note metal rim 979 and innerpolyethylene cup 980 of the acetabular component.

FIG. 9D illustrates a cross-section of a system where the interiorsurface 960 of the molded section 924 has teeth 962 or grooves tofacilitate grasping the neck of the femur.

After identification of the cartilage defect and marking of the skinsurface using the proprietary U-shaped cartilage defect locator deviceas described herein, a 3 cm incision is placed and the tissue retractorsare inserted. The cartilage defect is visualized.

A first Lucite block matching the 3D surface of the femoral condyle isplaced over the cartilage defect. The central portion of the Luciteblock contains a drill hole with an inner diameter of, for example, 1.5cm, corresponding to the diameter of the base plate of the implant. Astandard surgical drill with a drill guide for depth control is insertedthrough the Lucite block, and the recipient site is prepared for thebase component of the implant. The drill and the Lucite block are thenremoved.

A second Lucite block of identical outer dimensions is then placed overthe implant recipient site. The second Lucite block has a rounded,cylindrical extension matching the size of the first drill hole (andmatching the shape of the base component of the implant), with adiameter 0.1 mm smaller than the first drill hole and 0.2 mm smallerthan that of the base of the implant. The cylindrical extension isplaced inside the first drill hole.

The second Lucite block contains a drill hole extending from theexternal surface of the block to the cylindrical extension. The innerdiameter of the second drill hole matches the diameter of the distalportion of the fin-shaped stabilizer strut of the implant, e.g. 3 mm. Adrill, e.g. with 3 mm diameter, with a drill guide for depth control isinserted into the second hole and the recipient site is prepared for thestabilizer strut with a four fin and step design. The drill and theLucite block are then removed.

A plastic model/trial implant matching the 3-D shape of the finalimplant with a diameter of the base component of 0.2 mm less than thatof the final implant and a cylindrical rather than tapered strutstabilizer with a diameter of 0.1 mm less than the distal portion of thefinal implant is then placed inside the cartilage defect. The plasticmodel/trial implant is used to confirm alignment of the implant surfacewith the surrounding cartilage. The surgeon then performs finaladjustments.

The implant is subsequently placed inside the recipient site. Theanterior fin of the implant is marked with red color and labeled “A.”The posterior fin is marked green with a label “P” and the medial fin iscolor coded yellow with a label “M.” The Lucite block is then placedover the implant. A plastic hammer is utilized to advance the implantslowly into the recipient site. A press fit is achieved with help of thetapered and four fin design of the strut, as well as the slightlygreater diameter (0.1 mm) of the base component relative to the drillhole. The Lucite block is removed. The tissue retractors are thenremoved. Standard surgical technique is used to close the 3 cm incision.The same procedure described above for the medial femoral condyle canalso be applied to the lateral femoral condyle, the medial tibialplateau, the lateral tibial plateau and the patella. Immediatestabilization of the device can be achieved by combining it with bonecement if desired.

FIG. 10A illustrates a patella 1000 having a patellar ridge 1002,patellar facets 1004, 1004. Also depicted are the superior 1010,inferior 1012, lateral 1014, and medial 1016 surfaces.

FIG. 10B illustrates a mold drill guide 1020 from the perspective of thetibial matching surface 1022. The mold drill guide 1020 is configured sothat it is substantially a round cylinder. However, other shapes can beemployed without departing from the scope of the invention. Such shapescan be strictly geometrical, e.g. ovoid, or non-geometrical.

The tibial matching surface 1022 has an articular surfaces that matches,or closely conforms to, the surface of the patella. The design isproposed such that the guide is molded to precisely fit the anatomy ofthe articular surface of the patella for each patient, thus providingprecise location of the patella planning needed. As will be appreciatedby those of skill in the art, while an exact or precise fit is desired,deviations from a precise fit can occur without departing from the scopeof the invention. Thus, it is anticipated that a certain amount of errorin the design can be tolerated.

FIG. 10C illustrates the guide 1020 from the opposite perspective. Theplanar guide surface 1024 is depicted as flat, or substantially flat.However, as will be appreciated by those of skill in the art, othersurface configurations can be employed without departing from the scopeof the invention. Both FIGS. 10A and B depict apertures 1030, 1032. Acentral aperture 1030 is provided that accommodates, for example, a ⅛drill bit. The central aperture 1030 can be located such that it iscentered within the guide, off-centered, or slightly off-centered,without departing from the scope of the invention. An off-center orslightly off-center configure could be used with the round cylindricalconfiguration, but could also be used with the other configurations aswell. One or more additional apertures 1032 can be provided to enablepeg holes to be drilled. The apertures 1032 can be configured to have alarger diameter as the first aperture 1030, a smaller diameter, or anidentical diameter.

As shown in FIG. 10D the mold drill guide is fitted onto the articularsurface of the patella. Because the articular facing surface (shown inFIG. 10A) is configured to match or substantially match the articularsurface of the patella, the drill guide mates with the patellar surfaceto enable the drill holes to line-up in the desired place for theimplant. FIG. 10E illustrates the mold drill guide fitted onto thearticular surface of the patella with a ⅛″ drill 1050 positioned withinthe central aperture 1030.

Once a central aperture 1018 has been formed into the patella, a patellareamer 1060 is used to resurface the patella 1000. The reamer 1060 has aguide 1062, which fits within the aperture 1018, and a reamer 1064having a planing surface or blade surface 1066.

Turning to FIG. 11A the reamer 1060 is shown. The planning surface 1066has is configured to provide dual planing surfaces in order to recessthe patella and clear surrounding bone. Providing dual planing surfaceshelps to insure poly-metal articulation only. FIG. 11B illustrates thereamer relative to a patella. An area is prepared 1062 for a 30 mmpatella insert, and a surrounding area 1061 is reamed.

FIG. 12A illustrates a patella implant 1200. The inferior surface of theimplant 1200, has one or more pegs 1210. In this instance, the inferiorsurface 1202 is depicted with three pegs 1210. The implant 1200 ispositioned on a patella as shown in FIG. 12C such that a protuberance1220 on the superior surface 1204 of the implant is positionedapproximately at the apex of the natural patella. FIGS. 12D-F illustratethe implant superimposed within a patella, more clearly showing theprotuberance corresponding to the apex of the natural patella.

Also described herein are kits comprising one or more of the methods,systems and/or compositions described herein. In particular, a kit caninclude one or more of the following: instructions (methods) ofobtaining electronic images; systems or instructions for evaluatingelectronic images; one or more computer means capable of analyzing orprocessing the electronic images; and/or one or more surgical tools forimplanting an articular repair system. The kits can include othermaterials, for example, instructions, reagents, containers and/orimaging aids (e.g., films, holders, digitizers, etc.).

The foregoing description of embodiments of the present invention hasbeen provided for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseforms disclosed. Many modifications and variations will be apparent tothe practitioner skilled in the art. The embodiments were chosen anddescribed in order to best explain the principles of the invention andits practical application, thereby enabling others skilled in the art tounderstand the invention and the various embodiments and with variousmodifications that are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the followingclaims equivalents thereof.

The embodiments of the invention described above are intended to bemerely exemplary; numerous variations and modifications will be apparentto those skilled in the art. All such variations and modifications areintended to be within the scope of the present invention as defined inany appended claims.

1. A method of making a surgical tool, the method comprising: obtainingimage data associated with at least a portion of a joint; deriving asubstantially uncut cartilage surface associated with the joint from theimage data; deriving one of a mechanical axis and an anatomical axisassociated with the joint from the image data; and providing a surgicaltool that includes a contact surface for engaging the substantiallyuncut cartilage surface associated with the joint, the surgical toolfurther including at least one guide for directing movement of asurgical instrument in preparing an implant site, wherein providing thesurgical tool includes: shaping the contact surface based on the derivedcartilage surface such that the contact surface conforms to and issubstantially a negative of the derived cartilage surface; anddetermining position, shape and/or orientation of the at least one guidefrom the image data based, at least in part, on the one of a mechanicalaxis and the anatomical axis.
 2. The method according to claim 1,further comprising: positioning the at least one contact surface of thesurgical tool onto the joint surface; and directing movement of thesurgical instrument using the at least one guide.
 3. The methodaccording to claim 2, wherein directing movement of the surgicalinstrument includes making at least one of a cut, a drill hole, and areaming.
 4. The method according to claim 1, further comprisingadjusting the guide to the at least one position, shape and orientation.5. The method according to claim 4, wherein the surgical tool includes ablock that communicates with the at least one contact surface, the blockincluding the guide, wherein adjusting the guide includes: placing oneof a spacer and a shim between the at least one contact surface and theblock.
 6. The method according to claim 4, wherein adjusting the guideincludes using at least one of a ratchet mechanism, a hinge mechanism,and a jack mechanism.
 7. The method according to claim 1, whereinobtaining an image includes obtaining an MRI image.
 8. A method ofmaking a surgical tool, the method comprising: obtaining image dataassociated with at least a portion of a joint; deriving a substantiallyuncut cartilage surface associated with the joint from the image data;and providing a surgical tool that includes a contact surface forengaging the substantially uncut cartilage surface associated with thejoint, the surgical tool further including at least one guide fordirecting movement of a surgical instrument in preparing an implantsite, wherein providing the surgical tool includes: machining thecontact surface based on the derived cartilage surface such that thecontact surface conforms to and is substantially a negative of thederived cartilage surface; and determining position, shape and/ororientation of the at least one guide from the image data.
 9. The methodaccording to claim 8, further comprising: positioning the at least onecontact surface of the surgical tool onto the joint surface; anddirecting movement of the surgical instrument using the at least oneguide.
 10. The method according to claim 9, wherein directing movementof the surgical instrument includes making at least one of a cut, adrill hole, and a reaming.
 11. The method according to claim 8, furthercomprising adjusting the guide to the at least one position, shape andorientation.
 12. The method according to claim 11, wherein the surgicaltool includes a block that communicates with the at least one contactsurface, the block including the guide, wherein adjusting the guideincludes: placing one of a spacer and a shim between the at least onecontact surface and the block.
 13. The method according to claim 11,wherein adjusting the guide includes using at least one of a ratchetmechanism, a hinge mechanism, and a jack mechanism.
 14. The methodaccording to claim 8, wherein obtaining an image includes obtaining anMRI image.
 15. A method of making a surgical tool, the methodcomprising: obtaining image data associated with at least a portion of ajoint; deriving a substantially uncut cartilage surface associated withthe joint from the image data; and providing a surgical tool thatincludes a contact surface for engaging the substantially uncutcartilage surface associated with the joint, the surgical tool furtherincluding at least one guide for directing movement of a surgicalinstrument in preparing an implant site, wherein providing the surgicaltool includes: molding the contact surface based on the derivedcartilage surface such that the contact surface conforms to and issubstantially a negative of the derived cartilage surface; anddetermining position, shape and/or orientation of the at least one guidefrom the image data.
 16. The method according to claim 15, furthercomprising: positioning the at least one contact surface of the surgicaltool onto the joint surface; and directing movement of the surgicalinstrument using the at least one guide.
 17. The method according toclaim 16, wherein directing movement of the surgical instrument includesmaking at least one of a cut, a drill hole, and a reaming.
 18. Themethod according to claim 15, further comprising adjusting the guide tothe at least one position, shape and orientation.
 19. The methodaccording to claim 18, wherein the surgical tool includes a block thatcommunicates with the at least one contact surface, the block includingthe guide, wherein adjusting the guide includes: placing one of a spacerand a shim between the at least one contact surface and the block. 20.The method according to claim 18, wherein adjusting the guide includesusing at least one of a ratchet mechanism, a hinge mechanism, and a jackmechanism.